Mechanical Engineering Commons^™

Rans-Dns Simulations For Uncertainty Quantification In Dns Data Of Turbulent Mixing Layer, Mohamed Abuhegazy

Mechanical Engineering ETDs

Mixing layer flow is one of the canonical free shear flows in fluid dynamics. Such a flow is formed when two fluid streams move along one another with different velocities. Investigation of this flow development has been an active topic of research for many decades not only due to a wide range of environmental and technological applications where this flow may be observed, but also because of large discrepancies in the results obtained experimentally and numerically regardless this flow simple geometry. In this dissertation, the quality and uncertainty of extracted turbulent statistics of mixing layer flow are analyzed by applying …

Screw Dislocations In A Holed Wedge, Gregory T. Whiteside

Mechanical Engineering ETDs

A numerical code has been designed and implemented to find the stress at any material point in a holed-wedge material due to any number of crystal or real screw dislocations in the wedge. The code implements the image dislocation method together with the collocation point method to find stresses at any material point. We demonstrate that the combined analytical-numerical method (analytical with the image dislocations and numerical with the collocation-point method) is valid in that it produces stress fields giving rise to zero traction on free surfaces as well at an arbitrary number of collocation points on void surfaces. Additionally, …

Aerodynamic Dimpling For The Nose Cone Of A High-Power Competition Rocket, Graham Geoffrey Monroe

Mechanical Engineering ETDs

This thesis investigates nose cone dimpling for the reduction of the aerodynamic drag of a Level 3 High-Power amateur rocket. Two rocket launches were conducted. The first used a COTS nose cone with a smooth surface. A dimple distribution was created according to dimensions calculated by Sandia National Laboratories’ proprietary Right- Size Dimple Evaluator. A dimpled nose cone, designed with geometry matching the COTS component, was 3D printed. Axial acceleration and barometric pressure data, recorded by an onboard flight computer, were used to calculate and plot the drag coefficient as a function of the Reynolds number for the smooth and …

Main Effects Screening Study Of Fe/Kclo4 Thermal Battery Heat Pellet Resistive Activation, Bryan T. Steiner

Mechanical Engineering ETDs

Thermal battery iron-potassium perchlorate (Fe/KClO₄) heat pellets are often ignited by explosive igniters or heat paper. An alternative direct electrical ignition method via resistive heating is explored, which could improve thermal battery manufacturability and design flexibility. A main effects screening experiment was performed with the goal of confirming prior observed trends under more realistic test conditions and ranking the importance of design factors, to optimize future experiments and develop knowledge of the performance space. Relevant literature is examined to advance a theoretical understanding of resistive activation. Ignition sensitivity (go/no-go and time to ignition) and ignition energy are primary …

Control Of Fully-Actuated Aerial Manipulators And Omni-Directional Multirotors, Riley M. Mccarthy

Mechanical Engineering ETDs

This thesis details the system modeling, design, control, simulation, construction, and
testing of both a fully-actuated and omni-directional multirotor aerial system created
for the primary purpose of performing active tasks with their environment. This work
verifies the capabilities of both systems through empirical testing, and demonstrates
how through the use of new control methods and physical designs multirotors can
expand their purpose from passive inspection based tasks to active contact based
tasks. These systems take advantage of newly implemented control allocation features present in the PX4 flight control software, version 1.14. The use of which makes designing controllers for such …

Design, Fabrication And Characterization Of Zero Power Sensor/Harvester For Smart Grid Applications, Zeynel Guler

Mechanical Engineering ETDs

This study presents a flexible sensor/harvester device to be used in both electromagnetic sensing and energy harvesting applications for smart grids. When a current passes through a wire, the sensor detects the magnetic field created by that current. The sensor magnet interacts with the wire magnetic field resulting in a transfer of energy through the piezoelectric cantilever. Piezoelectric, conductive, magnetic, and magnetostrictive composite thin films were prepared to fabricate this device.

Initially, the magnet of the cantilever was optimized considering its shape, thickness, length, taper angle etc. via both simulations and experiments. Peak to peak voltage versus cantilever position graph …

Extremum Seeking Control Algorithms For Extremely High Frequency Antenna System Pointing, Scott Shore

Mechanical Engineering ETDs

The research examines the application of extremum seeking control (ESC) algorithms to ground station antenna pointing for extremely high frequency (EHF) communication systems. ESC algorithms search for local maxima or minima by locating where an objective function gradient goes to zero. With wireless communication expanding into higher frequencies, the ground station pointing requirement is increasing. ESC presents a method which utilizes available equipment and information to perform ground station pointing. Additionally, ESC algorithms do not rely on assumptions or approximations needed for other techniques. The dissertation demonstrates ESC algorithm feasibility for the ground station pointing problem, benchmarks the ESC algorithms …

Effect Of Fiber Proximity On The Pullout Response: A Finite Element Study, Tyler Mitchell

Mechanical Engineering ETDs

With the advancement of computational capabilities, there is growing interest in
developing intricate models for composite materials. This has been historically chal-
lenging due to the multifaceted interactions and failure mechanisms of these materi-
als. Multiscale modeling holds promise for predicting the intricate dynamics of such
materials. A foundational understanding of their microscale behaviors is critical, par-
ticularly the interfacial interactions between the fiber and matrix. This study delves
into the influence of fiber volume fraction (FVF) on fiber pull-out tests, focusing
on the impact of neighboring fibers across different geometries and the underlying
cohesive properties.

Analysis Of Ternary Chloride Salt Corrosion In High Nickel Alloys, Dimitri Madden, Gowtham Mohan

Mechanical Engineering ETDs

The United States Department of Energy seeks to improve the efficiency of concentrating solar power technologies by employing thermal energy storage with operating temperatures above 700°C. To meet these goals, the National Solar Thermal Test Facility at Sandia National Laboratories has considered the use of a ternary molten chloride salt for sensible heat storage systems. While favored for low cost, good heat transfer properties, and stability at high temperature, ternary chloride salt also exhibits high corrosive attack. Components of a chloride salt storage system would include piping, valves, tanks, pumps, receivers, and heat exchangers, which would be exposed to high …

Design And Development Of Magnetoelastic Resonators For Pv Ground Fault Detection, Skyler H. Oglesby

Mechanical Engineering ETDs

This project will design, fabricate, and test a magnetoelastic nickel-iron-cobalt alloy resonator for ground fault detection applications, specifically in photovoltaic systems. The electrodeposition technique will be used to fabricate the proposed resonator as it enables a precise manufacturing process. It allows for better control and optimization of material properties (magnetic, mechanical, and electrical) while facilitating the necessary dimensions. A great deal of study and experimentation will go into the electrolyte development when dealing with challenges like intrinsic stress and surface defects within the film. Hull cell analysis will be done to study the composition of the material in different electrochemical …

Mechanical Characterization Of Additively Manufactured Alloys Compared To Their Wrought Counterparts, Laith A. Alqawasmi

Mechanical Engineering ETDs

Additive manufacturing is a method of manufacturing based on building parts layer by layer, allowing for more control over shape of the product, therefore reducing machining costs, reducing material waste, faster production times and the ability to build complex engineering design that other manufacturing technologies won’t be able to produce. This research is on the tensile and indentation testing (following ASME standards) of 3D printed Ti-6Al-4V and Inconel 718 built by powder-based direct energy deposition technology. Ti-6Al-4V is an attractive material for the aerospace and aviation industry, and Inconel 718, a nickel-chromium based superalloy, is an attractive material for usage …

Development Of Models For The Velocity-Pressure Gradient Correlations In Incompressible Wall-Bounded Planar Turbulent Flows Using Multiple Linear Regression, Juampablo E. Heras Rivera

Mechanical Engineering ETDs

In this thesis, the multiple linear regression method is applied to clarify terms and their coefficients in data-driven models for velocity/pressure-gradient (VPG) correlations in the Reynolds stress transport equations. Additionally, a method for developing universal linear models for the VPG correlations with unchanging coefficients when complex conditions arise in a flow is introduced. The generated models were assessed using residual analysis to ensure an appropriate level of accuracy. Data from direct numerical simulation in an incompressible fully-developed turbulent channel flow at Re_tau = 392 with an adverse pressure gradient is used in the study as the data source.